<i>In vitro</i> colon fermentation of a traditional fermented food using stool from consumers and non-consumers

Traditional fermented foods (TFFs) spark debates about their potential health benefits as much is still unclear. Mostly conjectured as functional or living foods, TFFs are produced by live organisms through spontaneous or controlled fermentation processes. Here, we assessed the effect of exposure to Mabisi, a traditional Zambian fermented dairy food product, on the gut microbiota and production of short-chain fatty acids (SCFAs) in stool samples of consumers and non-consumers of Mabisi. We hypothesize that non-consumers of Mabisi will exhibit greater shifts in the gut microbiota composition and a more pronounced increase in SCFA production compared to Mabisi consumers. Stool samples of consumers and non-consumers of Mabisi were exposed to three treatments: (1) Mabisi, (2) fructooligosaccharides (FOSs) as a positive control, and (3) sterile water as a negative control. Treatments were digested using the <i>in vitro</i> INFOGEST static digestion model protocol 2.0 before anaerobic incubation for 24 h with the stool of consumers and non-consumers of Mabisi. We sequenced the hypervariable region (V3-V4) of the 16S rRNA gene to determine the microbial communities. We measured SCFA production as a proxy for gut microbiota functionality. Mabisi supplementation increased <i>Pediococcus</i> in both consumers and non-consumers of Mabisi compared to sterile water. After treatment with Mabisi, the gut microbiota of consumers showed greater resilience, with limited changes in community composition compared to non-consumers, as indicated by beta diversity (Mabisi consumers: <i>R</i>² = 0.07, <i>p</i>-adjusted = 0.375; Mabisi non-consumers: <i>R</i>² = 0.08, <i>p</i>-adjusted = 0.05) relative to their respective negative controls. Non-consumers were associated with higher production of SCFAs, including acetate, butyrate, formate and succinate, compared to Mabisi consumers. In conclusion, Mabisi has the potential to modulate <i>in vitro</i> gut microbiota by increasing beneficial bacteria and the production of SCFAs, with a particularly strong effect in non-consumers.